We plan to explore whether the highly successful attenuated yellow fever (YF-17D) vaccine, rDNA delivered by electroporation along with IL-12 and rAd35 can be used as vectors to express SIV proteins in a prime/boost regimen for vaccination against the AIDS virus. In a highly integrated series of experiments, we will first define the best viral targets for a vaccine. We will then bring the results together in a final efficacy experiment to test the vectors that, if successful, could prevent suffering by millions of people worldwide. Our application seeks to address four of the ten research areas outlined in the HIVRAD program announcement. Our project has the potential to impact HIV vaccine development on two fronts. First, we will define the targets of a successful vaccine in a challenge experiment. This will allow us to design a vaccine encoding the critical targets of a successful immune response. Second, we will develop three entirely novel vaccine vectors. If we are successful in this endeavor, our results will have a profound effect on HIV vaccine design.

Public Health Relevance

Completion of these studies should yield new methods of vaccine design. Furthermore, if any of our three vectors can effectively induce efficacious AIDS virus-specific immune responses in non-human primates, we could advance these vectors into human clinical trials. ******************************************************************************************************************** Project 1: Protective Immunity Project Leader: David Watkins (Description as provided by applicant) We hypothesize that a recombinant yellow fever vaccine (rYF) or rDNA (delivered by electroporation along with IL-12;EP+IL-12) prime followed by a recombinant adenovirus serotype 35 (rAd35) boost can control viral replication after either a homologous or heterologous AIDS virus challenge. We plan to test this hypothesis in macaques using rigorous challenges with the highly pathogenic SIV isolates, SIVmac251 and SIVsmE660. In a previous study, we found that a rDNA prime followed by a rAd5 boost (encoding all of the SIVmac239 proteins except for Env) reduced acute and chronic phase replication after a pathogenic SIVsmE660 mucosal challenge in six of eight vaccinated Indian rhesus macaques. Indeed, six of the vaccinees have no detectable viral replication at one year post challenge. This positive outcome is exceedingly rare in vaccine experiments using a pathogenic SIV challenge. We also discovered that vaccine-induced T cell responses against Gag and Vif correlated with this good outcome. We postulate that there are additional targets in the SIV proteome that can induce efficacious T cell responses. More recently our colleagues at lAVI have shown that vaccination with rDNA plasmids encoding all of the SIV proteins (including Env) by EP along with a plasmid encoding IL-12, followed by a rAd5 boost reduced viral replication of the highly pathogenic SIVmac239 challenge virus in seven of eight macaques. Indeed these vaccine results, along with the recent findings of Louis Picker using recombinant rhesus cytomegalovirus (rhCMV) vectors are the most encouraging non-human primate vaccine results to date. Our intention now is to perform a vaccine study to determine which of the SIV proteins are important as targets for the control of viral replication in our firs specific aim. In an attempt to improve upon these last two experiments we will also include newly discovered cryptic open reading frames (cORFs) in the vaccine. Our second specific aim is to determine whether a rYF or rDNA (EP+IL-12) prime followed by a rAd35 boost can control viral replication after either a homologous or heterologous AIDS virus challenge.